1. Field of the Invention
The present invention relates to a semiconductor memory, and particularly to a semiconductor memory that can effectively be used as a backup memory for storing data that is processed with the progress of a program being executed.
2. Description of the Prior Art
In general, it is possible to read data stored in a semiconductor memory simply by feeding it with an address signal and a read signal. In addition, most semiconductor memories are designed to be compatible between different manufacturers, that is, they are "standardized". Unfortunately, this has been prompting illegal duplication of programs stored in semiconductor memories and thus unauthorized use of the functions such programs offer.